1. Field of the Invention
The present invention relates generally to electrically bistable materials that can be converted from a low conductance (electrically off) state to a high conductance (electrically on) state by application of an electrical field to the material. More particularly, the present invention is directed to bistable materials that are composed of a polymer matrix in which nanoparticles are dispersed to provide the polymer with the desired bistable properties.
2. Description of Related Art
The publications and other reference materials referred to herein to describe the background of the invention and to provide additional details regarding its practice are hereby incorporated by reference. For convenience, the reference materials are numerically referenced and identified in the appended bibliography.
Nanometer materials exhibit peculiar electrical, optical and magnetic properties that are different from bulk materials and atoms [1-4]. The electronic materials in nanometer size are especially interesting due to the quantum effect of the electron. New phenomena have been observed on the nanometer materials, such as “Coulombic blockage”, surface-enhanced Raman signal, and size-determined energy gap. Charge transfer related the metal nanoparticle has gained much attention [5-8]. It was observed that metal nanoparticles can be charged positively or negatively. Charge transfer was observed on metal nanoparticles through electrochemical methods. Photo-induced charge transfer was also observed between the metal nanoparticle and the capped molecule or surrounding molecule.
Recently, we discovered that there is an electric-field induced charge transfer between gold (Au) nanoparticles capped with dodecanethiol and 8-hydroxyquinoline in a polymer film. [9] This electric-field induced charge transfer results in the formation of the film into two stable conductivity states. This electrically bistable film has very strong application potential as nonvolatile electronic memory. Our further effort was to study effect of the capped molecule on the electric-field induced charge transfer. The device with a polymer film containing 2-naphthalene-capped Au nanoparticles sandwiched between two aluminum (Al) electrodes exhibits an electrical transition to a high conductivity state under a high electric field. This device can be used as write-once-read-many electronic memory [11].